We are primarily concerned with understanding the rules governing formation of ordered retinotectal connections during Xenopus development. Using a combination of anatomical, electron microscopical and physiological techniques we are following development of optic fiber pathways during normal development and after optic nerve section. The experimental paradigms of eye rotation and compound eye formation are being used to perturb normal pathway development. We are also studying differences in growth and pathway slection behavior of regenerating and embryonic ganglion cell axons in vivo and in vitro culture systems. We are testing a spatio-temporal model of connectivity to determine whether simple morphogenetic rules governing cell birth and axon outgrowth can account for the formation of ordered neuronal arrays.